1. Field of the Invention
The present invention relates to a memory device.
2. Description of the Related Art
Semiconductor memory has become increasingly popular for use in various electronic devices. For example, non-volatile semiconductor memory is used in cellular telephones, digital cameras, personal digital assistants, mobile computing devices, non-mobile computing devices and other devices. Electrically Erasable Programmable Read Only Memory (EEPROM) and flash memory are among the most popular non-volatile semiconductor memories. During a programming or write operation, a series of program voltages is applied to a set of storage elements such as on a word line to raise the threshold voltages of the storage element to specified levels which represent programmed data states. Verify operations are performed after each program pulse to determine when each storage element has reached its intended state. During a read operation in such devices, a series of read reference voltages are applied to a set of storage elements to be read, and a determination is made as to which read reference voltage causes a storage element to become conductive. The read reference voltages are set to allow different data states of the storage elements to be distinguished.
However, errors can be caused during read operations due to factors such as electromagnetic coupling between storage elements which is a function of the storage elements' respective data states. Such coupling, which can raise the threshold voltage of a storage element after it has been programmed, is particularly problematic when repeated data patterns are written to the storage elements.